Paving materials such as asphaltic concretes that are used for roadways, parking areas, walkways and other traffic surfaces have been the subjects of much recent research. Some of these efforts have involved the addition of polymers, including plastics, in attempts to improve the flexibility, strength and life of the paving material. Other efforts have centered on recycling roadway asphalts in an effort to lower costs and reduce the environmental impacts such roadways have on our surroundings.
The increasing need to dispose of or find new uses for used or waste building materials (such as concrete, brick, gravel, rock and other debris) has led to growing costs and increased environmental concerns in the disposal of these materials.